(Jonathon Burch, Reuters) - Turkey has cancelled scheduled Turkish flights to its long-time rival Armenia, days before the first plane was due to take off, following fierce opposition from Turkey's ally and energy partner Azerbaijan.

The twice-weekly flights between Turkey's eastern city of Van and the Armenian capital Yerevan were due to begin on April 3 and, encouraged by a U.S. push for rapprochement, were meant to boost bilateral tourism and trade. But with just over a week until the first flight, and with tickets already on sale, Turkey's civil aviation authority stepped in and ordered the flights to be suspended.

Officials at Turkey's transport ministry confirmed the flights had been stopped but declined to give a reason. BoraJet, the private Turkish carrier set to fly the 45-minute route, has also declined to comment on the stoppage.

One BoraJet official twice denied the Van-Yerevan flights had ever been planned, even though the route was still available as a booking option on the firm's website on Monday.

Narekavank Tour, a Yerevan-based travel agency which has spent the last three years organizing the flights together with a Turkish travel agency in Van, said the reason was political. "The organizers were keen on staying away from politics. It is very sad and discouraging that Turkish authorities were not able to do the same and finally let politics interfere with this promising initiative," it said in a statement.

Asked if he thought this was due to specific pressure from Azerbaijan, Armen Hovhannisyan, co-founder of Narekavank Tour, said: "Of course, it's part of the whole formula, and maybe they have been working behind the scenes."

Officially at war, Armenia and Azerbaijan have been locked in a bitter dispute over the territory of Nagorno-Karabakh - a mountainous enclave within Azerbaijan with a majority Armenian population - which Armenian-backed forces seized along with seven surrounding Azeri districts in 1991. Turkey, which has never opened an embassy in Armenia, closed its land border in 1993 in a show of solidarity with Azerbaijan, a Muslim and Turkic-speaking ally which also supplies Ankara with billions of cubic meters of Caspian natural gas each year.

Azerbaijan has voiced fierce opposition to the flights and last week Ali Hasanov, a senior official at the president's office in Baku, said they amounted to support for "the occupant country" and only prolonged the "occupation".

"When such things are done by countries, which share the same strategic interests with Azerbaijan, we take it twice as fervently. It's not just our attitude, but an attitude of the whole Turkish society," Hasanov told Reuters.

A Turkish foreign ministry official said he was aware the flights had been cancelled but did not know the reason.

Turkey has sought to ease Azerbaijan's concerns over previous reconciliation moves by Turkey and Armenia, who are locked in their own decades-old dispute over whether ethnic Armenians killed by Ottoman forces during World War One were victims of systematic genocide. Rapprochement efforts have alarmed Azerbaijan which first wants to resolve the Nagorno-Karabakh dispute.

While Armenia's national carrier, Armavia, already operates flights to Istanbul and the coastal city of Antalya, the BoraJet flights would have would have given Armenians easier access to an area of Turkey they refer to as their "historical homeland". Once home to hundreds of thousands of Armenians, eastern Turkey is scattered with ancient Armenian historic sites, including a newly-restored medieval church on the small island of Akhtamar in Lake Van. The city of Van had large Armenian population prior to World War One.

Hovhannisyan, who has been organizing tours in eastern Turkey for years, said tourists currently had to travel by bus for up to 12 hours via Georgia before starting their excursion. "A lot of tourists can't go, either for health problems or comfort reasons. This was the original idea: If we had a direct flight we would be able to circumvent those problems," he said.

Hovhannisyan said they had written to the Turkish government asking them to reconsider their decision over the flights, which he said could also attract Turkish tourists to Armenia. "This is aimed at cooperation and peace. This is pure tourism. We don't want to have anything to do with politics."